The invention was not made by an agency of the United States Government nor under contract with an agency of the United States Government.
This invention relates to projectile-firing devices and particularly to methods of mitigating the recoil of such devices. More particularly, the present invention relates to utilizing friction for mitigating the recoil of a projectile-firing device designed to de-arm an explosives device, commonly known in the art as explosives disrupters.
In any gun system, or more generally, projectile-firing device, conservation of momentum provides that the momentum carried by the projectile and the gases is equal to, but in the opposite direction of, the momentum imparted to the device. The momentum imparted to the device is, in turn, equal to the recoil force integrated over time, or the impulse. This is commonly referred to as the xe2x80x9ckickxe2x80x9d experienced when a gun is fired. While the total amount of momentum for a given projectile fired at a given velocity cannot be changed, it can be managed. The force-time profile can be changed from a very high, short-lived force to a longer, much lower amplitude force pulse.
Present recoil-mitigation devices utilize complex and expensive hydraulics, pneumatics, pistons, springs, friction, or some combination thereof In addition, present devices are integral to the projectile-firing device and, therefore, not always easily or quickly adaptable to varying situations. Examples include U.S. Pat. No. 4,514,921 (coil spring compression), U.S. Pat. No. 4,656,921 (hydraulic fluid), U.S. Pat. No. 4,972,760 (adjustable recoil spring), U.S. Pat. No. 5,353,681 (recoil spring, friction, and pneumatics), and U.S. Pat. No. 5,617,664 (recoil spring).
In the particular case of some explosives disrupter devices for de-arming explosives devices, there may be no recoil mitigation. Disrupter devices are typically attached to a support frame mounted on the ground or mounted on a remote-controlled robot whereby the device can be triggered from a relatively safe distance to fire a projectile into an article suspected of containing a bomb or other explosive. Such devices are generally of a single-shot design and produce a significant impulse-oftentimes sufficient to propel the support frame/robot backwards, cause it to topple over, and/or sustain significant damage. Depending upon the situation, such devices may be called upon to fire a variety of projectiles at a variety of velocities from a variety of support frame/robots. This in turn creates a variety of recoil forces requiring, in turn, a variety of recoil mitigation solutions tailored to each support frame/robot. For example, the momentum imparted to the device from a column of water, often used to disarm soft-package bombs such as suspected briefcase bombs, may vary from close to 5 pounds-force-seconds at a low velocity to over 9 pounds-force-seconds at a high velocity (140 milliliter load at a velocity of 1000 feet per second) and even as high as 12 pounds-force-seconds. Metal slugs impart momentum in the range of 4 pounds-force-seconds to 6 pounds-force-seconds.
A general rule of thumb for a weapon without recoil mitigation fired by a human is that the momentum should not exceed 3 pounds-force-seconds. By comparison, the momentum carried by a 150 grain projectile fired from a 30-06 rifle at a velocity of 2810 feet per second is approximately 1.87 pounds-force-seconds. Thus, the momentum generated by an explosives disrupter can be relatively significant.
Therefore, there is a need for a recoil-mitigation device which overcomes these disadvantages.
According to the present invention, a recoil mitigation apparatus is provided. The apparatus includes brake shoes adapted to be interposed in a free space between a tube and the barrel of a projectile-firing device positioned coaxially therein. The brake shoes are laterally restrained relative to either the tube or the barrel, whereby when the projectile-firing device is fired, urging means create friction between the brake shoes and either the barrel or the tube respectively and, when the projectile is fired, the recoil is mitigated. Thus, it will be understood by those skilled in the art that the movement of the brake shoes may be first laterally restrained relative to the barrel and apply sliding friction to the inner surface of the tube. In the alternative, the brake shoes may be laterally restrained relative to the tube and apply sliding friction to the outer surface of the barrel. In either circumstance, when the projectile is fired, the recoil is mitigated.
In a preferred embodiment of the present invention, the barrel of a projectile-firing device is adapted to include a pair of flanges around the outer surface of the barrel. The flanges are in a facing, spaced-apart relationship such that a pair of substantially semi-cylindrical brake shoes is accommodated therebetween in a nesting position preventing lateral movement of the brake shoes relative to the barrel while allowing the brake shoes to move radially relative to the barrel. Coil or other suitable springs are provided between the edges of each brake shoe wherein the brake shoes are urged in an outward radial direction. When the projectile-firing device, brake shoe pair, and coil spring combination is positioned coaxially within an elongated tube and a projectile fired, the springs urge the brake shoes against the inner surface of the tube creating friction and thus the recoil is mitigated. A variety of springs and/or spacers to foreshorten the springs provides the flexibility needed to match the friction to a variety of recoil mitigation needs.
Accordingly, the principle object of the present invention is to provide a friction brake recoil mitigation apparatus that is readily adapted to a variety of supports, projectile-firing devices, projectiles, and projectile velocities for mitigating the recoil of such devices when the device is fired. Further objects, advantages, and novel aspects of the present invention will become apparent from a consideration of the drawings and subsequent detailed description.